This invention relates to air filtration systems for motorized vehicles, and in particular, to high performance air filtration systems for use with vehicles, such as Ford F-Series trucks having a V8, 7.3 L turbo-diesel engine.
The function of an air intake filter is to remove particulate matter from the intake air, so that clean air is provided to the engine. The intake air stream flows from the influent, or “dirty,” side of the filter to the effluent, or “clean,” side of the filter, with the air filter extracting the unwanted particles via one or more filter media layers. Filter media are selected to trap particles exceeding a particular size, while remaining substantially permeable to airflow over an expected filter lifetime.
The features and filter design choices that lead to improvements in one of these parameters (e.g., particle entrapment, airflow permeability, and filter lifetime) can lead to declines in the other performance parameters. Thus, filter design involves trade-offs among features achieving high filter efficiency, and features achieving a high filter capacity and concomitant long filter lifetime.
As used herein, filter efficiency is the propensity of the filter media to trap, rather than pass, particulates. Filter capacity is typically defined according to a selected limiting pressure differential across the filter, typically resulting from loading by trapped particulates. Volumetric filter flow rate, or flow rate, is a measure of the volume of air that can be drawn into a given filter having a particular effective filter area, efficiency, and capacity, at a particular point in the expected filter lifetime.
The choice of filter media having a high filter efficiency (wherein the filter media removes a high percentage of the particulate material in the intake air) is important, because any particulate matter passing through the filter may damage the engine. For filtration systems of equal efficiency, a longer filter lifetime typically is directly associated with higher capacity, because the more efficiently the filter medium removes particles from an air stream, the more rapidly that filter medium approaches the pressure differential indicating the end of the filter medium life. To extend filter lifetime, filter media can be pleated to provide greater filtering surface area.
The choice of air filter media that is permeable to airflow is important because the interposition of the filter into the engine intake air stream can impede the airflow rate. Decreased airflow rate tends to decrease engine efficiency, horsepower, torque, and fuel economy. Increased airflow rate through a vehicle's air filtration system, and/or the passage of cooler air therethrough, may improve engine performance. In applications demanding large volumes of filtered air, the ability to manipulate parameters such as air filter size, pleat depth, or both, is often constrained additionally by the physical environment in which the filter is operated (e.g., the space available for a filter of a given configuration within the engine compartment of a vehicle).
Some prior art air filters have been designed to provide increased filter flow rate. However, such designs may foster air turbulence at the filter inlet, which is an undesirable quality which may ultimately impair airflow. Also, some existing filter designs employ abrupt topological transitions, such as a one-step ring, a ledge, an edge, or a peak, which tend to encourage the development of air eddies and to reduce airflow into the filter. When air eddies cause influent air to bypass regions of the filter media near these abrupt transitions, the effective area of the filter available for filtration is reduced.
Prior art filters using pleated media often secure one or both ends of the pleated media to a filter housing in such a manner that the pleats are forced together, such that air cannot flow between adjacent pleats. In this situation, the effective area of a pleated filter media available for filtration is reduced.
As can be seen, there is a need for an improved air filtration system for an internal combustion engine for achieving high efficiency filtration of intake air. Furthermore, there is a need for an improved filtration apparatus for achieving high volumetric airflow rate and maximum effective area available for filtration.